►Glyphosate (N-(phosphonomethyl)glycine) is an effective foliar-applied herbicide with broad-spectrum activity. Greenhouse and laboratory experiments were conducted to determine the importance of soil moisture, autoclaved soil,…
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▼Glyphosate (N-(phosphonomethyl)glycine) is an effective
foliar-applied herbicide with broad-spectrum activity. Greenhouse
and laboratory experiments were conducted to determine the
importance of soil moisture, autoclaved soil, soil type, sphagnum
peat, soil pH, added phosphorus, and plant residues on crop
establishment and growth when glyphosate was applied before
emergence of the crop.
Glyphosate was applied preemergence with a track-mounted
sprayer in 281 or 374 L/ha spray volume. Counts and fresh weights
were taken to determine the effect of the glyphosate application.
Radiolabelled glyphosate was used to determine Freundlich
adsorption isotherms for Chehalis, Crooked, and Semiahmoo-2 soils
at various pH or phosphorus levels.
Glyphosate application to sandy soils (Chehalis and Crooked)
reduced fresh weight of Italian ryegrass (Lolium multiflorum Lam.),
whereas application to finer-textured soils seldom caused plant
injury, indicating that soil texture may be an important factor. Also, on Chehalis and Crooked soils, increasing the soil pH caused
increased injury to Italian ryegrass, suggesting that more
glyphosate was available at higher soil pH. This was confirmed in
an adsorption study using radiolabelled glyphosate. Other
interactions also should be considered. The incidence of damping-off
(Pythium spp.) was higher on plants grown in glyphosate-treated
Chehalis soil than plants grown in untreated soil.
Barnyardgrass (Echinochloa crusgalli (L.) Beauv.) and Italian
ryegrass were injured by a preemergence application of glyphosate
to sphagnum peat. However, glyphosate application to muck
(organic) soils did not injure bioassay species. These results
suggest that nondecomposed organic matter does not render
glyphosate unavailable, and therefore, caution is advised when
applying glyphosate to media with sphagnum peat or other
nondecomposed plant material.
Adjusting soil moisture, autoclaving soil, or adding
phosphorus did not influence glyphosate availability in soil.
Dead or dying perennial ryegrass residues, whether chemically
treated or not, reduced fresh weight of Italian ryegrass seedlings.
Roots or whole plant residues were more inhibitory than shoots.
Increasing the time interval between treating perennial ryegrass
and planting Italian ryegrass reduced phytotoxicity to Italian
ryegrass. Adding fertilizer to pots to alleviate competition for
nutrients did not prevent the phytotoxic effect of perennial
ryegrass residues. Experiments exposing ryegrass seedling roots or shoots to
various concentrations of glyphosate, in the absence of soil,
showed that roots were damaged more than shoots when roots were
treated with glyphosate. However, roots and shoots were injured
equally when shoots were treated with glyphosate, indicating that
glyphosate is readily translocated to the roots.
Italian ryegrass and bentgrass (Agrostis tenuis Sibth.
'Highland') were more sensitive to glyphosate applied preemergence
than crimson clover (Trifolium incarnatum L.), alfalfa (Medicago
…
Advisors/Committee Members: Appleby, Arnold P. (advisor), Bolton, Floyd (committee member).

▼ Bean shoot parts that respond to glyphosate (N-
(phosphonomethyl)glycine) in ways useful for bioassay were determined
by applying glyphosate doses of 3.8 to 60.3 ug ae per plant to the
simple leaves when the first trifoliolate leaflets were about 1 cm
long. Dry weights of parts that were almost fully enlarged at
treatment were greater in treated than untreated plants after two
weeks. Maximum weight increase was found with the 15.1 ug dose.
Growth of younger shoot parts was reduced by glyphosate, showing linear
reductions with log dose from 3.8 to 30.2 ug. Growth reduction of
young shoot parts was therefore concluded to be a better measure of
sublethal glyphosate activity than reduction of total shoot growth.
Using the above assay, growth of bean plants from a controlled
environment was evaluated after treatment with a 3.0 mM glyphosate
solution applied in uniform drops of 138, 430, and 1230 um diameter.
The largest drops were less effective than both smaller sizes, and no
difference in activity between the two smaller sizes was found. Bean
plants grown outdoors in pots responded similarly to a 12.2 mM
glyphosate solution applied in drops of 138, 240, 430, 740, and 1230 um
diameter. There were no activity differences between the four smallest
sizes, and the 1230 um size was less effective than all others.
To ascertain effects of leaf coverage on glyphosate activity, 1.0
ul drops of glyphosate solution were applied to the simple leaves of
bean plants and physically spread with the tip of a small, glass rod to
cover areas of different size. Herbicidal activity was reduced with
increased drop spread on plants grown in a controlled environment, but
not with plants grown outdoors. Cuticular adsorption of glyphosate was
assumed not to be a factor in reducing activity because isolated leaf
cuticles from beans grown both outdoors and in a growth chamber were
shaken in an aqueous solution of ¹⁴C-glyphosate at 25 C and showed no
adsorptive tendency throughout an 83-hour period.
The hypothesis that glyphosate applied in low volumes is more
effective because of reduced leaf surface contact is not supported by
drop size data, and is supported only by results from controlled
environment treatments showing less activity from increased drop
spread.
Advisors/Committee Members: Crabtree, Garvin D. (advisor).

► An aqueous solution of technical glyphosate [N-(phosphonomethyl) glycine] was applied in homogeneous sprays of 120, 180 and 300 μm droplets to seedlings of a bush…
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▼ An aqueous solution of technical glyphosate [N-(phosphonomethyl)
glycine] was applied in homogeneous sprays of 120, 180 and 300 μm
droplets to seedlings of a bush type green bean (Phaseolus vulgaris
L. 'OSU 1604') at a carrier rate of 20 1/ha. At each droplet size
all combinations of 3 dosage levels of glyphosate, with or without
the addition of a non-ionic surfactant (X-77), were compared. Plant
growth decreased as glyphosate dosage increased. There was no significant
effect of adding surfactant. When compared with 180 μm droplets,
approximately 2.2 times and 1.6 times as much active ingredient was
needed to give a 50% growth reduction with 120 and 300 μm droplets,
respectively.
A preliminary study of effect of surfactant concentration on
glyphosate toxicity indicated both surface tension and contact angle
of the spray solution had no significant relation to the phytotoxicity
of the herbicide spray. Surfactant (X-77) enhanced the phytotoxicity
of glyphosate most at the concentration of 0.1% v/v.
Advisors/Committee Members: Crabtree, Garvin D. (advisor).

► <p class=MsoNormal><span class=SpellE>Glyphosate</span>-resistant (GR) Italian ryegrass has been documented in many different countries around the world and has now become a major problem in row…
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▼ <p class=MsoNormal><span class=SpellE>Glyphosate</span>-resistant (GR) Italian
ryegrass has been documented in many different countries around the world and
has now become a major problem in row crop production areas of
Mississippi.<span style='mso-spacerun:yes'> </span>Field experiments were
conducted from 2006 to 2008 in the Mississippi Delta to evaluate various
herbicide and tillage treatment programs for its control.<span
style='mso-spacerun:yes'> </span>
<p class=MsoNormal>Highest level of control and reduction of GR Italian
ryegrass biomass was observed with mechanically incorporated as well as surface
applied residual herbicides in the fall of the year.<span
style='mso-spacerun:yes'> </span>Control of GR Italian ryegrass was 86-95%
with surface applications of <span class=SpellE>clomazone</span> at 0.56, 0.84,
and 1.12 kg <span class=SpellE>ai</span>/ha, <i style='mso-bidi-font-style:
normal'>s</i>-<span class=SpellE>metolachlor</span> at 1.79 kg <span
class=SpellE>ai</span>/ha and KIH-485 at 0.16 kg <span class=SpellE>ai</span>/ha
171 days after emergence.<span style='mso-spacerun:yes'> </span>Using a
systems approach, <span class=SpellE>preplant</span> incorporated (PPI) <span
class=SpellE>clomazone</span> and/or <i style='mso-bidi-font-style:normal'>s</i>-<span
class=SpellE>metolachlor</span> followed by <span class=SpellE>preemergence</span>
(PRE) application of <span class=SpellE>paraquat</span> + <span class=SpellE>linuron</span>+
non-ionic surfactant was also found to control and reduce biomass of GR Italian
ryegrass.
Advisors/Committee Members: Vijay Nandula (chair), Daniel Poston (chair), Clifford Koger (committee member), Steve Martin (committee member).

► Field experiments were conducted at Carman, Manitoba to determine the effect of tank-mixing different contact herbicides with glyphosate and time of application of harvest aid…
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▼ Field experiments were conducted at Carman, Manitoba to determine the effect of tank-mixing different contact herbicides with glyphosate and time of application of harvest aid herbicides on residue accumulation in dry bean seed and the effect of tank-mixing a contact herbicide with glyphosate on weed control. Carfentrazone-ethyl in mixture with glyphosate was the least effective harvest aid herbicide and did not fully desiccate plant parts or reduce glyphosate residues in the seed to less than 2 ppm. Saflufenacil, diquat, flumioxazin, and glufosinate in mixture with glyphosate effectively desiccated all plant and reduced glyphosate residue accumulation in the seed. Saflufenacil in mixture with glyphosate provided the most consistent efficacy on three weed species. Time of application of harvest aid herbicides influenced residue accumulation and yield; however, all harvest aids applied at or after 75% pod colour change had no negative effect on yield and significantly reduced the risk of residue accumulation.
Advisors/Committee Members: Gulden, Robert (Plant Science) (supervisor), Ayele, Belay (Plant Science) Farenhorst, Annemieke (Soil Science) (examiningcommittee).

Waddell, K. (2014). The evaluation of new harvest aid herbicides for dry bean (Phaseolus vulgaris L.) production in Manitoba. (Masters Thesis). University of Manitoba. Retrieved from http://hdl.handle.net/1993/23239

Waddell K. The evaluation of new harvest aid herbicides for dry bean (Phaseolus vulgaris L.) production in Manitoba. [Masters Thesis]. University of Manitoba; 2014. Available from: http://hdl.handle.net/1993/23239

University of Guelph

6.
Follings, Joanna.
CONTROL AND DISTRIBUTION OF GLYPHOSATE RESISTANT GIANT RAGWEED IN ONTARIO.

▼ Giant ragweed (Ambrosia trifidia) was the first glyphosate resistant weed in Canada. Giant ragweed interference in soybean has resulted in yield losses of greater than 90%; therefore, control of this competitive weed is essential. In 2011 and 2012, glyphosate resistant giant ragweed was confirmed at 34 additional sites Ontario. In addition, there are 11 locations confirmed with cloransulam-methyl resistant giant ragweed and 5 locations with multiple resistance to both glyphosate and cloransulam-methyl. Glyphosate resistant giant ragweed has been found in four additional counties. Field trials were conducted at 5 locations in 2011 and 2012 to determine the most effective control options. Based on these experiments, glyphosate tankmixes with 2,4-D or amitrole provide the most effective control. These two tankmixes provided greater than 90% control. The minimum dose of 2,4-D required for acceptable control of glyphosate resistant giant ragweed is 500
g a.e. ha-1.
Advisors/Committee Members: Sikkema, Peter (advisor), Tardif, François (advisor).

The weed is among the species of greatest importance in the fields of different cultures. Because it is a species that has a high power to produce thousands of seeds that have adapted to the use of herbicides, their study becomes very important to mitigate the damage to crops. The work was to study the morphological and physiological characteristics of species Conyza canadensis (L.) Cronquist for resistance to the herbicide chemical group of glycines substituted in plants with a history of…

►Glyphosate resistant Kochia scoparia is a growing concern in Canada, and is increasing in incidence. Trials were conducted in naturally occurring glyphosate susceptible kochia populations…
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▼Glyphosate resistant Kochia scoparia is a growing
concern in Canada, and is increasing in incidence. Trials were
conducted in naturally occurring glyphosate susceptible kochia
populations or in areas seeded with glyphosate susceptible kochia
seed. By looking at herbicides with different modes of action that
can control kochia as effectively as glyphosate, as well as
introducing a new herbicide application window, it may be possible
to decrease the occurrence of glyphosate-resistant kochia biotypes
from becoming the majority of kochia populations on the Canadian
prairies. Fluroxypyr + MCPA ester (a group 4 herbicide), bromoxynil
+ 2,4D (a combination of group 6 and 4 herbicides), saflufenacil
and carfentrazone-ethyl (group 14), pyrasulfotole + bromoxynil (a
combination of group 27 and 6 herbicides) were as effective at
controlling kochia as glyphosate when applied pre-seeding. It was
determined that herbicide effectiveness varies according to
location. Introducing a new window of herbicide application in the
fall, post-harvest, was not effective at controlling
kochia.

► With the recent confirmation of glyphosate-resistant Amaranthus species in many important agronomic regions of the United States, a study was initiated to identify and document…
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▼ With the recent confirmation of glyphosate-resistant Amaranthus species in many important agronomic regions of the United States, a study was initiated to identify and document the occurrence of glyphosate resistant common waterhemp in East-central Texas. Accessions of several suspected glyphosate-resistant biotypes of common waterhemp were grown in a greenhouse before receiving rates of glyphosate from 434 to 3468 g ae ha^-1. Dose-response analyses were conducted to provide LD50 values for each accession. LD50 values ranged from 387 to 4549 g ae ha^-1 glyphosate.
A study evaluating the efficacy of twelve different weed control programs for common waterhemp and Palmer amaranth control in cotton was conducted in Burleson County, TX in 2012 and 2013. The study was conducted in cotton possessing stacked glyphosate-, glufosinate-, and dicamba-tolerant technologies. Preplant and preemergence treatments included fomesafen, pendimethalin, prometryn, pyrithiobac, S-metolachlor, and trifluralin. These treatments were followed by a variety of early- and mid-postemergence treatments. Preplant and preemergence treatments resulted in 81 to 100% control of Palmer amaranth and common waterhemp with the exception of pyrithiobac, which provided only 29 to 60% control of these species. Following early- and mid-postemergence applications, 92 to 100% control of these species was obtained. Applications of pendimethalin PRE followed by pyrithiobac EPOST and glufosinate MPOST in 2013 provided lower control of both species (92 to 93 %) than all other treatments evaluated in the study 14 days after MPOST applications.
With the potential commercialization of synthetic auxin-tolerant crops, there is an increased need for understanding of the influence of spray nozzle design and herbicide formulation on physical spray drift reduction. A study was conducted in a low speed wind tunnel utilizing laser diffraction technology to analyze the droplet size spectra produced by different spray nozzles and herbicide formulations. Nozzles utilizing a pre-orifice design or a combination of pre-orifice and air-inclusion design were observed to produce significantly larger spray droplets than those without these features. Herbicide formulations were shown to have a significant influence on droplet size as well. Different herbicide formulations were observed to decrease the production of drift-prone fine droplets by as much as 64%.
Advisors/Committee Members: Baumann, Paul A (advisor), Morgan, Gaylon D (committee member), Dotray, Peter A (committee member), Lyons, Robert K (committee member).

► Interest and research on herbicide-resistant cropping systems has increased dramatically since the introduction of glyphosate-resistant crops in 1996. New advances in herbicide-resistant cropping systems,…
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▼ Interest and research on herbicide-resistant cropping systems has
increased dramatically since the introduction of glyphosate-resistant crops in
1996. New advances in herbicide-resistant cropping systems, such as dicambaresistant
soybean and cotton, provide opportunities to help alleviate selection
pressure currently applied by glyphosate-only systems. While there is no doubt
dicamba-resistant genetics will have a huge impact on production practice, there
are questions that must be answered about possible interactions with dicamba
and glyphosate tank mixtures. The primary objectives of this research were to
evaluate the effect of glyphosate/dicamba combinations on common Mississippi
weed species, as well as determine effects of these combinations on absorption
and translocation of dicamba.
Four monocots: johnsongrass, barnyardgrass, large crabgrass, and
broadleaf signalgrass; and four dicots: sicklepod, hemp sesbania, prickly sida,
and pitted morningglory, were chosen to represent troublesome weed species.
Plants were sprayed at the 4±1 leaf stage with glyphosate, dicamba, and
combinations of the two herbicides. Rates were chosen with the goal of achieving
40 to 70% control in order to determine synergistic/antagonistic responses.
Antagonism was observed in each species tested. Increasing rates of both
herbicides alleviated the antagonism in most weeds. A synergistic response was
observed in all graminaceous species and pitted morningglory when herbicide
rates increased.
Barnyardgrass and sicklepod were selected to quantify absorption and
translocation of 14C-dicamba in order to account for interactions observed from
tank-mix combinations. Rates for dicamba and glyphosate were selected based
on results from the interaction study. Dicamba, glyphosate, and tank-mix
combinations were applied to sicklepod and barnyardgrass before treatment with
14C-dicamba. Plants were harvested 4, 12, 24, and 72 h after treatment. The
addition of glyphosate to dicamba resulted in reduced translocation of 14C-dicamba
in both species. While the data did indicate a translocation interaction,
glyphosate and dicamba combinations effectively overcame antagonism effects
when higher rates were applied on sicklepod and barnyardgrass.
Advisors/Committee Members: Dr. David R. Shaw (chair), Dr. Clifford H. Koger (committee member), Dr. Marshall B. Wixson (committee member), Dr. Jason A. Bond (committee member), Dr. Joseph H. Massey (committee member), Dr. Krishna N. Reddy (committee member).

► ENGLISH ABSTRACT: Glyphosate remains an important herbicide in weed control. This is due to several positive attributes it has including sytemicity, wide spectrum of weed…
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▼ ENGLISH ABSTRACT: Glyphosate remains an important herbicide in weed control. This is due to several positive
attributes it has including sytemicity, wide spectrum of weed control and environmental
friendliness. Its efficacy and lack of residual activity are therefore important to ensure
adequate weed control without imposing hazards to the environment. Despite these favourable
attributes for weed control glyphosate has its shortcomings.
Evolution of resistance to glyphosate has been a major concern from 1996. However,
there are other factors that reduce the maximum potential of glyphosate. Any factors that
reduce glyphosate efficacy may result in the target plant being subjected to non-lethal
concentrations of glyphosate. This in turn may predispose the plants to developing herbicide
resistance. Some factors that may influence efficacy of glyphosate, and therefore be possibly
selecting for resistance were investigated in this study.
Although glyphosate is a postemergence herbicide, its efficacy is not exempt from the
effect of soil and nutrients in which the weeds occur. The possibility of this occurring was
investigated in a greenhouse study on ryegrass (Lolium spp.) In this study ryegrass was grown
in three soils: pure sand (SS), soil from pasture paddock (PS) and soil from crop field (CS).
The soils varied in nutrient composition and, although all were classified as sand, they had
varying proportions of sand, loam and clay. This investigation consisted of four experiments.
The first experiment was investigating the effect of growing a susceptible commercial
ryegrass cultivar on PS, CS and SS soils on the efficacy of glyphosate (360 g a.i. L-1
formulation) applied at five glyphosate application rates (GAR). The GARs were 0 (0x), 67.5
(1/8x), 135 (1/4x), 270 (1/2x) and 540 (1x) g a.i. ha-1. The second experiment investigated the
effect of growing a susceptible commercial ryegrass cultivar and a glyphosate resistant
ryegrass biotype on PS and CS soils on the efficacy of glyphosate. The application rates were
0 (0x), 270 (1/2x), 540 (1x), 1080 (2x) and 2160 (4x) g a.i. ha-1. The third and the fourth
experiments were similar to the first experiment except: The latter investigated the role of
nutrient content of irrigation water (pure water or balanced nutrient solution) and; the former
investigated the effect of soil activity (by covering the soil surface with cotton at the time of
spraying) of glyphosate with regard to the role it plays on efficacy of glyphosate. Our findings
showed that: i) soil affects the efficacy of glyphosate with more control (19% survivors) found in the PS soil compared to 50% and 62% survivors in CS and SS soils respectively, this effect
may be dependent upon the species resistance as; ii) the effect in the resistant ryegrass biotype
was reversed with about 95% of survivors in the PS soil compared to about 78% in CS soil;
iii) efficacy of glyphosate is influenced by the soil nutrient status and the nutrient content of
the irrigation water. This was shown by…
Advisors/Committee Members: Pieterse, P. J., Stellenbosch University. Faculty of AgriSciences. Dept. of Agronomy..

► There is increasing evidence of a deep integration between microbes and human physiological function. With such extensive communication in both directions, it is arguable that…
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▼ There is increasing evidence of a deep integration between microbes and human physiological function. With such extensive communication in both directions, it is arguable that a major disruption on either side would have substantial impact on the other. A number of modern diseases have been associated with shifts in the microbiome populations such as inflammatory bowel disease, diabetes, acne vulgaris, etc. However, which initiates the other often remains unclear. From the standpoint of dysbiosis preceding the pathologies, it presents a route by which environmental exposures can indirectly impact human physiology. This idea pertains in particular to compounds like the herbicide glyphosate which is alleged to be non- toxic to human cells. Because this compound has been demonstrated to impact bacteria, it presents a whole other layer of consideration in regards to its potential to cause disease in humans. While studies have been done to assess impact of this compound on different microbial communities with mixed results, none seem to have examined impact on human microflora specifically. This thesis examines the association between the dysbiosis and human disease from the angle of disease occurring as an effect of the dysbiosis. Ultimately, the hypothesis is that glyphosate exposure is sufficient to induce many modern diseases via disruption of the microbiome as illustrated in Figure 1. Furthermore, included here are proposed future experiments to explore glyphosate’s potential to perturb the microbiome..
Advisors/Committee Members: Lopez, Gerardo (advisor), Lybarger, Lonnie (advisor), Lantz, Clark (committeemember).

The global area planted with transgenic crops was 125 million hectares in 2008. Of this total, 53% was occupied by soybean modified for tolerance to glyphosate. The rapid acceptance of this technology is due to high efficiency, low cost and easy to implement. However, the abuse use of a broad spectrum herbicide can cause direct and indirect impacts. The direct…

► Experiments were carried out at the Experimental Station of Coimbra, Minas Gerais, of the Department of Plant Science of the Universidade Federal de Viçosa to…
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▼ Experiments were carried out at the Experimental Station of Coimbra, Minas Gerais, of the Department of Plant Science of the Universidade Federal de Viçosa to study the effect of Mo in mixture with glyphosate, applied on corn and brachiaria straw on bean plant crop under no-till system. Two field assays were carried out, the first on brachiaria straw and the second on corn straw. The experiment was set up in split-plots, with the plots consisting of five doses of molybdenum (0, 100, 200, 400 and 800 g ha-1), applied in combination with the a desiccating herbicide (glyphosate) and the split-plots consisting of two doses of molybdenum (0 and 100 g ha-1), applied via the leaves on the bean plant, in the DBC, with four repetitions. Each split-plot was composed by five 5 m long, 0.5 m spaced lines of bean plant, cultivar Ouro Vermelho. Molybdenum foliar fertilization was carried out at stage V4, with sodium molybdate (39% of Mo) being the source of Mo. The content of chlorophyll was evaluated in the third completely expanded leaf from the apex (index leaf), through the SPAD index (Soil Plant Analyses Development), with three readings per leaflet being carried out in ten leaves randomly selected from the split-plot plants. The contents of N, P, K, Ca, Mg, S, Mn, Zn, Cu and Mo were evaluated in the leaves and grains under laboratory conditions. The number of plants per hectare (NP), number of pods per plant (NPP), number of grains per pod (NGP), mass of 100 grains (MG) and yield (Y) were later determined. The bean plant cultivated on the brachiaria straw absorbed MO applied on the latter, combined with glyphosate, increasing its yield. The content of Mo in the leaves increased in response to the application of the micronutrient, in mixture with glyphosate. Its concentration was even greater in the grains, when Mo was also applied via the leaves. The foliar content of nitrogen increased with the application of Mo mixed with glyphosate, when the micronutrient was not applied on the bean plant leaves, presenting a behavior similar to the SPAD index. When, besides the mixture of Mo with glyphosate, the former was applied via the leaves on the bean plants, these two factors decreased slightly. P content in the grains reduced when Mo was applied via the leaves. The content of K in the grains increased with the increase of the molybdenum dose, applied together with glyphosate on the brachiaria straw. On the other hand, when the bean plant was cultivated on the corn straw, the number of pods per plant (NPP) increased in response to the application of the Mo mixtures with glyphosate, when there was no foliar application of Mo on the bean plant. The foliar content of Mo was higher in the treatment Mo was applied on the bean plant leaves, regardless of the dose of this micronutrient, mixed with glyphosate. The content of Mo in the grains increased linearly with the increase of the micronutrient dose, applied together with glyphosate. The SPAD index was not altered, regardless of the Mo dose applied together with glyphosate, and/or…
Advisors/Committee Members: Paulo Roberto Cecon, José Eustáquio de Souza Carneiro, Rogério Faria Vieira, Geraldo Antônio de Andrade Araújo, Renildes Lúcio Ferreira Fontes.

► Kochia [Kochia scoparia (L.) Schrad.] is a weed of great economic importance in the Great Plains and western United States and Canada. This weed is…
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▼ Kochia [Kochia scoparia (L.) Schrad.] is a weed of
great economic importance in the Great Plains and western United
States and Canada. This weed is prone to evolving resistance to
herbicides. Glyphosate is the most widely used herbicide in
glyphosate-resistant crops and chemical fallow, and is extremely
valuable to crop production. Anecdotal reports of kochia control
failure with glyphosate in western Kansas arose during the
mid-2000’s. The objectives of this research were to (1) confirm and
characterize glyphosate resistance in kochia and measure its impact
in western Kansas, (2) gather information on grower weed management
practices before and since glyphosate resistance in kochia was
confirmed, and (3) determine if altered absorption and
translocation of glyphosate contributes to glyphosate resistance in
kochia. Dose-response studies on greenhouse and outdoor grown
plants, and shikimate accumulation assays confirmed one kochia
population collected in 2007 and eight populations collected in
2010 tolerated three- to eleven-times more glyphosate compared to a
known glyphosate-susceptible (GS) population. Furthermore, 40
kochia populations collected in 2012 showed varied response, from
slightly elevated tolerance to resistance to 0.84 kg ae ha-1
glyphosate. Further analysis suggested these populations were at
different stages of resistance evolution. An online survey revealed
that growers increased glyphosate use rate and application
frequency, but decreased exclusive use of glyphosate and
diversified weed management practices during post- compared to
pre-glyphosate confirmation periods. Most survey respondents
reported presence of glyphosate-resistant (GR) kochia in at least
in few fields, and half reported GR kochia in a majority of fields.
Thus, together with the resistance confirmation studies, it is
estimated that at least one-third of western Kansas kochia
populations have evolved resistance to glyphosate. Nominal
differences in absorption and translocation of 14C-glyphosate
observed between GS and GR kochia populations likely do not
contribute to differential response of these populations to
glyphosate. Glyphosate-resistant kochia has become widespread in
western Kansas in a short period of time. Use of weed resistance
best management practices (BMP) is imperative to sustain the
utility of glyphosate in the region.
Advisors/Committee Members: Phillip W. Stahlman.

►Glyphosate resistant Canada fleabane (GRCF) exists in Ontario due to the repeated use of glyphosate on Roundup Ready crops. GR weeds must now be managed…
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▼Glyphosate resistant Canada fleabane (GRCF) exists in Ontario due to the repeated use of glyphosate on Roundup Ready crops. GR weeds must now be managed using an integrated approach including herbicides like, 2,4-D choline/glyphosate DMA, a premixed herbicide solution. The objective of this research was to determine the ideal application timing of 2,4-D choline/glyphosate DMA herbicide for the control of GRCF. Single applications of 2,4-D choline/glyphosate DMA (1720 g ae ha-1) provided 71-93% control, while sequential applications provided 98-100% control of GRCF 8 WAA. S-metolachlor (1600 g ai ha-1) + flumetsulam (50 g ai ha-1) + clopyralid (135 g ae ha-1) applied preemergence provided the best consistent control of GRCF (95-99%) of the preplant corn residual herbicides evaluated. 2,4-D choline/glyphosate DMA applied post-emergence provided 97-100% control of GRCF following any preplant corn residual herbicide. The size of the GRCF (10, 20 and 30 cm tall) at the time of the 2,4-D choline/glyphosate DMA application did not affect the efficacy of the herbicide. The 2,4-D choline/glyphosate DMA formulation and a tank mix of 2,4-D amine and glyphosate DMA provide equivalent control of GRCF.
Advisors/Committee Members: Sikkema, Peter (advisor), Robinson, Darren (advisor).

▼ Farmers in southern Ontario face a significant threat from glyphosate-resistant weeds such as Canada fleabane and giant ragweed. Left uncontrolled, glyphosate-resistant weed interference in soybean can result in substantial yield loss. The three objectives of this study were: 1) to determine the biologically effective rate of isoxaflutole, metribuzin, and glyphosate on glyphosate-resistant Canada fleabane and giant ragweed biotypes, 2) to assess the response of isoxaflutole and glyphosate applied as a tank-mix on glyphosate-resistant and glyphosate-susceptible biotypes of both species, and 3) to ascertain the response of isoxaflutole, metribuzin and glyphosate tank-mix on the glyphosate-resistant biotypes of both species. In growth room experiments, antagonism is observed at low rates of glyphosate plus isoxaflutole in glyphosate-susceptible giant ragweed and at field rates of the same tank-mix in glyphosate-resistant Canada fleabane. The addition of metribuzin to the tank-mix resulted in an additive or synergistic response across all rates in the glyphosate-resistant biotypes of both species tested. Field experiments confirmed the additive and synergistic response of the three-way tank-mix in both species tested. An estimated 631 (126+504) and 420 (84+336) g a.i. ha-1 of isoxaflutole plus metribuzin in a 1:4 ratio are required for control of glyphosate-resistant giant ragweed and Canada fleabane respectively.
Advisors/Committee Members: Tardif, Francois (advisor), Sikkema, Peter (advisor).

This dissertation reports the study of two resistance mechanisms in a glyphosate-resistant Conyza canadensis population (B15), comparatively with a susceptible population (B), from intensive olive orchards in Alentejo (south of Portugal). Initially, the presence of resistance was confirmed by a shikimate leaf disc assay. Then, the sequence of the gene encoding the enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) was determined and, lastly, were analysed the expression levels of the gene encoding this enzyme.
The shikimate leaf disc assay showed a higher accumulation of shikimate in the population B, relatively to population B15, 24 hours after being exposed to glyphosate. The EPSPS-2 cDNA sequencing didn’t reveal differences in enzyme’s constitution between the two populations. The analysis of gene expression also revealed no differences in expression levels of this enzyme, 24 hours after glyphosate application.
These results suggest that the studied population has no EPSPS enzyme mutation or overexpression as a mechanism of resistance to glyphosate

► Phragmites australis, the common reed, is an invasive macrophyte in many eastern North American wetlands. Reed often rapidly forms dense, near-monotypic stands by replacing native…
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▼ Phragmites australis, the common reed, is an invasive
macrophyte in many eastern North American wetlands. Reed often
rapidly forms dense, near-monotypic stands by replacing native
vegetation, which lowers plant diversity and alters wetland habitat
structure. Accordingly, herbicides such as imazypr-based Habitat®
and glyphosate-based AquaNeat® are often applied to reed stands in
an attempt to control its establishment and spread. Although these
herbicides are apparently not toxic to benthic organisms, they may
indirectly affect them by altering available habitat structure via
increased detrital litter, increased light penetration to surface
waters and increased water temperature. Understanding the impacts
of widespread herbiciding on benthic communities, as well as the
impact of different herbicides on habitat conditions, should help
wetland managers design control plans to reduce reed and conserve
system biodiversity. I compared gastropod (i.e., snails) and
epiphyton communities, and habitat conditions among large,
replicated plots of unsprayed Phragmites, glyphosate-sprayed
Phragmites, imazapyr-sprayed Phragmites and unsprayed Typha
angustifolia (narrow-leaf cattail) in early the summer 2008 in a
Lake Erie coastal marsh. I studied gastropods because they can
greatly influence trophic structure in freshwater systems by
consuming benthic algae and by serving as prey to sportfish.
Moreover, I included Typha angustifolia in the study because it is
another invasive plant common to many Lake Erie coastal wetlands.
Relative abundances of gastropods were similar among treatments on
24 June and 30 June, but differed on 8 July. On 8 July, Fossaria
spp. were particularly abundant in herbicide-treated plots, and
Promenetus umbilicatellus was abundant in AquaNeat®- treated plots.
Snail densities were greater in plots containing metaphyton
(filamentous green algae) than in plots without metaphyton, and
juvenile and small snails were abundant in metaphyton mats.
Metaphyton presence was linked to increases in light penetration
caused by herbiciding. Epiphytic algal densities, and chlorophyll a
levels, an indicator of algal biomass, were low in all treatments,
and diatom-dominated epiphyton communities were similar among
treatments. Dry mass of benthic organic matter (BOM), which can
provide available substrate for epiphyton growth and habitat for
snails, was also similar among treatments. Dissolved oxygen and
water depths were similar among treatments, but water depths
significantly declined with sampling date. A combination of low and
highly variable water levels, low oxygen levels, and eutrophic
conditions apparently shape snail and algal community structure in
this marsh. My results suggest that both glyphosate- and
imazapyr-containing herbicides have little effect on the
herbivore-producer relationship and gastropod diversity in Sheldon
marsh 1-year post-spraying.
Advisors/Committee Members: Holomuzki, Joseph R. (Advisor).

The objective of this study was to determine the efficacy of this herbicide in two populations of Conyza bonariensis, one suspected of resistance (B8) and a susceptible one (C), from olive groves and citrus orchards in Alentejo, south of Portugal. Assays were performed on germination agar medium, glyphosate dose-response assays in petri dishes with different concentrations of glyphosate and a greenhouse (1) and laboratory (2) study were conducted (1) to confirm and characterize glyphosate resistance and (2) to determine whether resistant and susceptible populations have differential shikimate accumulation. Population B8 showed significant higher germination and emergence than population C but lower mortality rate. Dose–response studies revealed that the suspected resistant population was two- to three-fold less sensitive to glyphosate than the susceptible population. The dose-response flazasulfuron assay with whole plant in the rosette stage revealed the doses were completely effective on both populations. Shikimate accumulation was higher in resistant population at 72-h after treatment, for the recommended concentration of glyphosate. However, it was lower for concentrations of 360 g ha-1. These results pointed that population B8 is resistant to glyphosate and flazasulfuron is an option for the chemical control of resistant populations.

▼ Animals use chemical cues for signaling between
species. However, anthropogenic chemicals can interrupt this
natural chemical information flow, affecting predator- prey
interactions. I explored how a glyphosate-based herbicide
influenced the reactions of <i>Pardosa milvina</i>, a
common wolf spider in agricultural systems, to its predators, the
larger wolf spider, <i>Hogna helluo</i> and the carabid
beetle, <i>Scarites quadriceps</i>. First, I tested the
effects of exposure to herbicide and chemical cues from these
predators on the activity, emigration, and survival of <i>P.
milvina</i> in laboratory and mesocosm field experiments. In
the presence of <i>H. helluo</i> cues in the
laboratory, <i>P. milvina</i> always decreased activity
and increased time to emigration. However, in the presence of
<i>S. quadriceps</i> cues, these spiders only decreased
activity and increased time to emigration when herbicide was also
present. Presence of predator cues and herbicide did not affect the
emigration of <i>P. milvina</i> from field mesocosms,
but survival was highest for spiders exposed to <i>S.
quadriceps</i> cues alone and lowest for those exposed to
herbicide alone. Secondly, I tested the effects of predator cues,
herbicide and prey availability on foraging and reproduction in
female <i>P. milvina</i>. Spiders offered more prey
captured and consumed more, while those exposed to <i>H.
helluo</i> cues consumed less. Availability of prey and
exposure to predator cues and herbicide in foraging trials had
interactive effects on <i>P. milvina’s</i> subsequent
reproductive success. In the low prey treatments, exposure to
predator cues and herbicide each reduced reproductive success. In
the high prey treatments, exposure to herbicide reduced
reproductive success for spiders also exposed to <i>S.
quadriceps</i> cues, but increased reproductive success for
spiders also exposed to <i>H. helluo</i> cues. Finally,
I exposed juvenile <i>P. milvina</i> to <i>S.
quadriceps</i> cues and herbicide but found no effect of
either on the spider’s growth and development. Together, these
results indicate that predation risk and herbicide application
likely interact in complex ways to affect the movement,
reproduction and survival of a major arthropod predator in
agricultural systems, and thus may have complex effects on the food
web.
Advisors/Committee Members: Rypstra, Ann (Advisor).

► Under Louisiana climatic conditions, production of sugarcane (Saccharum spp.) is limited to a maximum growth period of nine months. To increase sucrose concentration in the…
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▼ Under Louisiana climatic conditions, production of sugarcane (Saccharum spp.) is limited to a maximum growth period of nine months. To increase sucrose concentration in the crop, ripener is applied prior to harvest. The chemical ripeners, glyphosate and trinexapac-ethyl were applied to the sugarcane cultivars HoCP 96-540, L 99-226, L 99-233, HoCP 00-950, and L 01-283 eight weeks prior to harvest. When glyphosate was applied at 210 g ae/ha, TRS for the cultivars was increased 10 to 28% compared with the nontreated. Increases in TRS with glyphosate were greatest for HoCP 96-540 and L 99-226 and least for HoCP 00-950 and L 01-283. Trinexapac-ethyl at 350 g ai/ha increased TRS for the cultivars 7 to 10% and increases were greatest for L 99-233 and least for HoCP 00-950. Sugarcane yield averaged across cultivars was reduced 9% with glyphosate and 7% for trinexapac-ethyl at 350 g/ha. An increase in sugar yield per hectare, a function of TRS and sugarcane yield, was observed only when glyphosate was applied to HoCP 96-540 (16% increase) and when trinexapac-ethyl at 300 g ai/ha was applied to L 01-283 (13% increase). In a second study where eight cultivars were harvested six weeks after glyphosate application, TRS for HoCP 96-540 was increased an average of 10% compared with the nontreated and sugarcane yield was decreased 17%; sugar yield was not affected. In another study, sugarcane yield, TRS, and sugar yield were not affected by nitrogen rates of 67, 112, and 157 kg/ha. Six weeks after application of glyphosate at 210 g/ha TRS averaged across N rates was 11% greater than the nontreated and 9% greater than when trinexapac-ethyl was applied at 350 g/ha. TRS following trinexapac-ethyl was equivalent to the nontreated. Sugarcane yield and sugar yield were not affected by ripener application. In a separate study TRS and sugar yield were not affected when glyphosate or trinexapac-ethyl was applied in 75 and 150 L/ha spray volume or when none or 0.25% v/v surfactant was added to the spray solution. Averaged across spray volume and surfactant treatments, TRS was as much as 8% greater for glyphosate compared with trinexapac-ethyl.

► A dearth of knowledge exists regarding occupational glyphosate exposures among amenity horticulturalists. Glyphosate is the highest volume herbicide used globally, and has recently been classified…
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▼ A dearth of knowledge exists regarding occupational glyphosate exposures among
amenity horticulturalists. Glyphosate is the highest volume herbicide used globally,
and has recently been classified by the International Agency for Research on Cancer
as a 2A 'probably carcinogenic to humansâ. The objective of this study was to
characterise glyphosate exposures and identify exposure determinants among amenity
horticulturists.
Human biomonitoring assessments were completed by collecting spot urine samples
from workers. In parallel, a dermal and inadvertent ingestion study was completed by
collecting wipe samples of the workerâs hands and perioral region and by analysing
samples of worker gloves. Samples were analysed using liquid chromatography
tandem mass spectrometry (LC-MS/MS). Linear mixed effect regression models were
constructed to evaluate determinants of dermal, inadvertent ingestion and total
glyphosate exposure.
A total of 205 urine samples and 351 wipe and glove samples were collected and
analysed for glyphosate across 69 work tasks involving the glyphosate based pesticide
products. Glyphosate concentrations ranged from below the limit of quantification to
10.66 Î¼g Lâ1; the human biological half-life was estimated to be 5 Â½ to 10 hours. Peak
exposure levels were identified in urine samples collected up to three hours after
cessation of the pesticide task. A forward built mixed effect model including sampling
time, participant age and application type explained 62% of the variability in worker
hand glyphosate concentrations. In the inadvertent ingestion exposure model the
determinants hand contamination, the frequency of hand to mouth and surrounding
area contact and sampling time explained 50% of the variability in perioral
concentration. Combined hand and perioral region concentrations explained 40% of
the variability in the urinary glyphosate concentrations (Î¼g L-1).
Occupational glyphosate exposures among amenity horticulturalists are higher than
expected from environmental exposure alone and comparable with agricultural
studies. New information is reported on the human biological half-life of glyphosate.
Advisors/Committee Members: Coggins, Marie, Irish Commissioner of Public Works, The Colt Foundation UK, Health and Safety Authority (HSA), Ireland.

►Glyphosate resistant weeds have evolved because of over-reliance on this herbicide without integration with other effective weed control methods. Since the first incidence of glyphosate…
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▼Glyphosate resistant weeds have evolved because of over-reliance on this herbicide without integration with other effective weed control methods. Since the first incidence of glyphosate resistance in 1996, 24 weed species have been confirmed with glyphosate resistance in 18 countries. Australia is one of the countries that is most affected by glyphosate resistance with resistance reported in 6 weed species. Glyphosate resistance in L. rigidum remains the greatest problem with 347 documented populations. These resistant populations have mostly been reported from cropped situations with heavy glyphosate use, such as chemical fallows, orchards, and vineyards. Recently populations of glyphosate resistant L. rigidum have started appearing on fence lines where glyphosate is applied once annually late in the cropping season. The aim of this project was to investigate the evolution and management of glyphosate resistance in L. rigidum on fence lines. Dose response of L. rigidum to glyphosate was investigated in two fence line populations from Clare, South Australia (Clare 2010 and Clare 2009), two known resistant populations (SLR 76 and SLR 77) and one susceptible population (SLR 4). In these experiments, the susceptible population (SLR4) was completely controlled at the recommended glyphosate rate of 450 g a.e ha ⁻ ¹. However, the resistant populations required much higher rates of glyphosate to achieve control. The fence line populations required 9 to 15-fold higher glyphosate dose to achieve 50% weed kill (LD₅₀) than SLR4. The standard resistant population SLR 77 had 5 to 7- fold greater resistances than SLR4, while SLR 76 was 20 to 30-fold more resistant than the susceptible control. The pattern of glyphosate translocation in L. rigidum plants was investigated by examining the movement of ¹⁴C-labeled glyphosate. There were no significant differences between L. rigidum populations in the amount of herbicide absorbed 48 hours following application. Plants of populations SLR 76, Clare 2009 and Clare 2010 retained significantly more herbicide in their treated leaves than did the susceptible plants 48 h after the treatment. The amount of herbicide translocated to the stem and untreated leaves of the susceptible plants was significantly greater than that translocated into these tissues in the resistant plants. These differences in translocation pattern of glyphosate in these fence line populations of L. rigidum suggest that resistance is associated with an altered translocation mechanism. The pattern of glyphosate translocation in SLR 77 was similar to the susceptible population SLR4 indicating presence of a different resistance mechanism. To determine if these fence line populations have target-site mutation, the populations were assayed through DNA sequencing to determine any alterations in the EPSPS gene. Results from this screening indicated, the fence line populations did not have a mutation at Pro 106 of the ESPS gene observed in glyphosate resistant weeds with target site resistance. A famer survey was conducted on…
Advisors/Committee Members: Preston, Christopher A. (advisor), Gill, Gurjeet Singh (advisor), School of Agriculture, Food and Wine (school).

► Kochia (Kochia scoparia (L.) Schrad) is a troublesome weed throughout the western United States and Great Plains. It is an aggressive warm season annual dicot…
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▼ Kochia (Kochia scoparia (L.) Schrad) is a troublesome
weed throughout the western United States and Great Plains. It is
an aggressive warm season annual dicot plant that exhibits
protogynous flowering and facultative open pollination. The
aggressive growth habit and prolific seed production enable kochia
to spread and compete well for light, moisture, and nutrients.
Kochia is ranked as one of the most problematic weeds in cultivated
fields including corn, sorghum, wheat, soybean, and sugarbeet.
Kochia has been found to lower yields as well as hinder mechanical
harvest. Glyphosate is a nonselective herbicide that is widely used
in controlling kochia in no-till cropping systems. With rapid
adoption of no-till systems where glyphosate is used for weed
burndown treatment before planting and extensive use of glyphosate
resistant crops, it is common that glyphosate is frequently applied
on the same field during the growing season. In 2007, poor control
of kochia was observed in three fields in Western Kansas.
Greenhouse experiments were conducted with 10 kochia populations to
determine the efficacy of glyphosate on kochia when applied at 10
different rates and at 3 plant heights. Herbicide rates included 0,
0.0625, 0.125, 0.25, 0.50, 1, 1.5, 2, 4 and 6 times a typical use
rate of 870 g ae/ha. Resistance to glyphosate was identified in
three kochia populations. The glyphosate resistant populations from
Ingalls, Norton, and Moscow Kansas were 4.6, 3.3, and 2.8 times
more resistant to glyphosate than a susceptible population,
respectively, based on the rate required for 50% control.
Glyphosate injury symptoms included stunting, and chlorosis,
followed by some necrotic tissue but resistant plants generally
recovered from injury, or were slow to show symptoms. In general,
the level of resistance is greater in more developed plants
compared to younger plants. Experiments also were conducted on the
different kochia biotypes to evaluate glyphosate absorption and
translocation, and any differences in mineral content of the plants
that might be detrimental to glyphosate activity. Differences in
glyphosate absorption and translocation and kochia mineral content
were not sufficient to explain the resistance to
glyphosate.
Advisors/Committee Members: Kassim Al-Khatib.

► Freshwater ecosystems are often exposed to intense agricultural pollution, which can impact species interactions such as those between parasites and their hosts. I studied the…
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▼ Freshwater ecosystems are often exposed to intense agricultural pollution, which can impact species interactions such as those between parasites and their hosts. I studied the effect of glyphosate (the active ingredient of a widely-used agricultural herbicide, Roundup®) on the proliferation and transmission of trematode parasites in the New Zealand mud snail, Potamopyrgus antipodarum. This ubiquitous and highly abundant snail serves as the first intermediate host to a wide diversity of trematodes. Trematode larval stages multiply within the snail to form free-living infective stages known as cercariae which then go on to infect native invertebrates, fish and birds. Earlier evidence suggested that herbicides from agricultural run-off might weaken the immune system of the snail and promote the within-snail multiplication of the trematode Telogaster opisthorchis. I tested the effect of long-term exposure to different levels of glyphosate on snail behaviour, cercarial production by three trematode species parasitic in P. antipodarum, and cercariae survival. Glyphosate had an effect on snail behaviour, however infection by an undescribed renicolid trematode did not. Snails exposed to the pollutant were hidden more than their conspecifics in the control treatment. Exposure of snails to glyphosate doubled, and in some cases tripled, cercarial output in three trematode species, i.e. the previously-mentioned renicolid, Coitocaecum parvum, and Apatemon sp.. In addition, survival time of renicolid cercariae was 1.57% greater when glyphosate was present at moderate concentrations. The more a parasite’s quality and quantity increase, the more likely we will see cascading effects on other hosts (fish, amphibians and molluscs). My results provided evidence that there are indirect effects from agricultural run-off on freshwater systems, and add weight to the pressure on the agricultural sector to limit the large-scale use of herbicide.
Advisors/Committee Members: Poulin, Robert (advisor).

► A survey was conducted by phone to nearly 1,200 growers in six states (Illinois, Indiana, Iowa, Mississippi, Nebraska, and North Carolina) in 2005. The…
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▼ A survey was conducted by phone to nearly 1,200 growers in six states (Illinois,
Indiana, Iowa, Mississippi, Nebraska, and North Carolina) in 2005. The survey measured
producers cropping history, perception of glyphosate-resistant (GR) weeds, past and
present weed pressure, tillage practices, and herbicide use as affected by the adoption
of GR crops. The objectives of this study were to determine the effect of GR crop use
on producers tillage practices; changes in herbicide use patterns after adoption of a GR
crop; effect of grower awareness of GR weeds on sources of information growers use;
and growers perceptions on resistance management based on knowledge of GR weeds
in their farming operation.
The adoption of GR cropping systems contributed to large increases in the
percentage of growers using no-till and reduced-till systems. Tillage intensity declined
more in continuous GR cotton and GR soybean (45 and 23%, respectively) than in
rotations that included GR corn or non-GR crops. Tillage intensity declined more in the
states of Mississippi and North Carolina than in the other states, with 33% of the growers
in these states shifting to more conservative tillage practices after the adoption of a GR
crop. This was in part due to the lower amount of conservation tillage adoption in these
states prior to GR crop availability.
With respect to herbicide use patterns, frequently used herbicides for fall
applications were 2,4-D and glyphosate; these herbicides were often used for preplant,
burndown weed control in the spring. As expected, crop rotations using GR crops had a
high percentage of respondents that made one to three POST applications of glyphosate
per year. Overall, glyphosate use has continued to increase, with concomitant
decreases in utilization of other herbicides.
Concerning grower awareness of GR weeds and perceptions of resistance
management in 2005, the majority of the growers (88%) were aware of a weeds
potential to develop resistance to glyphosate, while 44% were aware of state-specific,
documented cases of glyphosate weed resistance. Growers that have had experience
with GR weeds were more knowledgeable about resistance management practices that
could be used to mitigate them.
Advisors/Committee Members: David R. Shaw (chair), Clifford H. Koger (committee member), John D. Madsen (committee member), John D. Byrd (committee member), Michael E. Newman (committee member).